1. Field of the Invention
The present invention relates to an image processing apparatus for outputting a projection image to a display unit in an image display apparatus that projects the projection image onto a projection surface by using an image projecting means having an optical system.
2. Description of the Related Art
In liquid crystal projector apparatus, rear projection television sets, and other such projection display apparatus, factors such as the positional relationship between the projection light source and the screen and aberration in the optical system may produce image distortion (keystone distortion). Methods of correcting this distortion by projecting an image that has been transformed with characteristics inverse to the distortion are known.
In one of these methods, the image is corrected by electrical signal processing; in a liquid crystal projector apparatus described in Japanese Patent Application Publication No. H8-102900 (in particular, paragraph 0047, FIG. 3), keystone distortion is corrected by linear interpolation between adjacent pixels in the scanning lines of an input video signal.
In the prior art referred to above, the frequency characteristic of the filter selected for interpolation may produce patterns, causing problems of image quality.